The prior art has traditionally delivered topically effective pharmaceutical agents in creams, lotions and gels, all of which require the user to soil his fingers and hands in the application of such medicaments and in the subsequent action of "rubbing it in". Further, such products are greasy, slow to dry and inevitably leave a residue which not only is visible, but rubs off onto clothing and the like, all of which are discomforting to the social ease of the user.
One variation from the traditional creams, lotions and gels occurred with the development of the so-called stick delivery systems which were used to apply anti-perspirants, deodorants, lip balm, lip coloring and like ingredients which are generally applied to the surface of the skin.
Antiperspirant sticks based on the combination of a volatile silicone, a fatty alcohol and a powdered antiperspirant were recently developed and marketed. These sticks, however, have not been extended beyond simple antiperspirant sticks using water soluble inorganic antiperspirant salts. This limited use is the result of the known mechanism of antiperspirant vehicles and the need to intentionally design such delivery systems so as to limit the amount of active ingredient (antiperspirant) which can penetrate into the skin. For an antiperspirant to be efficacious, a large concentration of the active ingredient must be maintained on the surface of the skin from whence it is slowly dissolved and diffused into the apocrine ducts, rather than being absorbed through the skin. To extend this prior art to other pharmacologically active topical agents, it is necessary to greatly enhance the amount of the drug which is able to penetrate through the skin to reach the desired sites of action. This absorption of a drug through the skin is referred to as percutaneous absorption.
Nor does the typical lip balm formulation solve the problem because such products normally contain large amounts of wax (such as Beeswax, Carnauba, and the like), and oils, (such as, castor oil, lanolin and the like), whereupon a greasy/oily sensation is created on the skin which is not only unpleasant but gives the user the feeling of being "dirty". In addition, this type of formulation, as with antiperspirants, severely limits the percutaneous absorption of most drugs through the skin.
Likewise, the conventional creams and lotions fail to obviate the problems enumerated because the creams and lotions are excessively greasy and have the potential to sequester the active ingredient so that the percutaneous absorption of the drug and its efficacy is reduced.
Accordingly, one object of the present invention is to develope a consumer acceptable delivery system for applying pharmaceuticals and cosmetics to the human skin which avoids the aforesaid disadvantages of the prior art creams, lotions, gels and sticks while enabling the user to readily control its application to a specified location with maximum effectiveness, a minimum of waste, and no mess.
Another object of the present invention is to provide a silky and non-greasy delivery system which is capable of spreading a drug or cosmetic evenly and smoothly on the skin and which leaves virtually no residue.
A further object of the present invention is to provide a new and improved delivery system which is compatible with a broad range of dermatologically effective pharmaceuticals and is capable of delivering such pharmaceuticals with high efficiency and increased percutaneous absorption thereby increasing both the bioavailability of the active ingredient and its efficacy.
These and still further objects as shall hereinafter appear are fulfilled by the present invention in a remarkably unexpected fashion as will be readily discerned from a careful consideration of the detailed description of certain exemplary embodiments thereof which hereafter appear.